Producing all skin viscose rayon



Hired sweghlaswmQ i PRODUCING ALL SKIN'VISCOSE RAYON Byron A. Thumm,Prospect Park, Pa., assignor to American Viscose Corporation,Philadelphia, Pa., a corporation of Delaware No Drawing. Filed Nov. 3,1954, Ser. No. 466,677 8 Claims. (Cl. 18--'54) This invention relates tothe production of shaped bodies of regenerated cellulose from viscoseand more particularly tofilaments and fibers of regenerated cellulosefrom viscose.

In the conventional methods of producing shaped bodies ofregenerated-cellulose from viscose, a suitable cellulosic material suchas purified cotton linters, wood pulp,-mixtures thereof, and the like isfirst converted to an alkali cellulose by treatment with a caustic sodasolution and after shredding the treated cellulose material, it isallowed to age/The aged alkali cellulose is then converted to a xanthateby treatment with carbon disulfide. The cellulose xanthate issubsequently dissolved in a caustic soda solution in an amountcalculated to provide a viscose of the desired cellulose and alkalicontent. After filtration, the viscose solution is allowed to ripen andis subsequently extruded through a shaped orifice into a suitablecoagulating and regenerating bath. In the production of shaped bodiessuch as filaments, the viscose solution is extruded through a spinneretinto a coagulating and regenerating bath consisting of an aqueous acidsolution containing zinc sulfate. The filament may subsequently bepassed through a hot aqueous bath where it is stretched to improve itsproperties such as tensile strength. The filamentmay then be passedthrough a dilute aqueous solution of sulfuric acid and sodium sulfate tocomplete the'regene'ration of the cellulose, in case it is notcompletely regenerated upon leaving the stretching stage. The filamentis subsequently subjected to washing, purification, bleaching, possiblyother treating operations and drying," being collected either before orafter these treatments; it p The filaments as formedby the conventionalmethods, consist of a skin or outer shell portion, and a core por tionwith a sharp line of demarkation between thetwo. The cross-section ofthe filaments exhibits a very irregular or crenulated exterior surfacewhen even small amounts of zinc salts or certain other polyvalent metalsalts are present in the spinning bath. The skin and core portions ofthe filament represent differences in structure and these differentportions possess different swelling and staining characteristics, thelatter permitting a ready identification of skin andcore. The sharplyirregular and crenulated surface structure has a relatively low abrasionresistance and readily picks up foreign particles such as dirt. Althoughthe core portion possesses a relatively high tensile strength, it haslowabrasion resistance and a 10W flex-life, is subject to fibrillation andis relatively stifi, It has now been discovered thatthe' presence ofsmall amounts of water-soluble alkylene .oxide' adducts of aniline inviscose, in the spinning bath; or in both the viscose and the bathresults in the production of shaped V t 7 p v Iii/ 1$ being dissolvednsthe caust c solution or. to the bodies of regenerated cellulose snchas filaments, films, sheets and the like composed ofall iskin andfhaying im proved properties and characteristicsfpfoviding'ftliat theamount of the adduct is maintained certain limits certain compositionlimits. which will bevdefined i The most readily distinguishable charachereinafter. teristics' as compared to conventional filamentsinclude a smooth, non-crenulated surface and the filaments consistentirely of skin. This invention contemplates the use of alkylene oxideadducts of aniline having from about 2 to about 50 or more alkyleneoxide groups per molecule, preferably from about 4 to about 30 alkyleneoxide units per molecule of aniline. It is obvious that for allpractical purposes considering cost, ease of preparation. commercialavailability and solubility in water, ingalkali solutions and in acidsolutions, the ethylene oxide adducts are preferred. Theoretically, analkylene oxide adduct such as ethylene oxide adduct of anilinecontaining 4 ethylene oxide units permolecule of aniline would consistof a compound in which each of the amino hydrogen atoms has beenreplaced With a chain of two ethylene oxide units. It is not necessary,however,-that all of the amino hydrogens be replaced nor isit necessarythat the ethylene oxide chains replacing the different hydrogen atoms bethe same in each instance. The term adduc is used herein to simplify thedisclosure and description and designates a water-soluble N-substitutedaniline formed by the reaction between an alkylene oxide and anilinewherein the alkylene oxide or a polyoxyalkylene chain replaces one orboth of the hydrogen atoms attached to the nitrogen atom. It is notnecessary to employ individual specific compounds of 2,975,020; Prev ew1 1961 i the type described and the reactionproducts which-probablyconsist of a mixture of specific compounds, the

average alkylene oxide content per molecule of anilinev being Within thestated ranges, are satisfactory.

Where, for example, each of the amino hydrogen atoms has been replacedwith an alkylene oxide group,

the compound is a N,N-di(beta-hydroxyalkyl)aniline.

Whereone of the amino hydrogen atoms has been-replaced with apolyalkylene' glycol radical, the compound ,7 4

is a N-mono(omega-hydroxy polyoxalkylene) aniline, Compounds in whichboth amino hydrogen atomshave been replaced with alkylene Ioxide chainsare ,N,N+di- (omega-hydroxy polyoxyalkylene) anilines. I

The production of all skin products requires that; eer

tain minimum amounts of the alkylene oxide adduct be insolution in theviscose or in the spinning bath. There:

fore, the alkylene oxide adduct must have sufiicient solu- V bility topermit the minimum amount of the adduct'to 1 be dissolved in theviscose'or the spinning bath or both.

The adduct may be conveniently added to the viscosex in the form of asolution in alkali or water and to the spinning bath in a solution ofwater or of the spinning bath; Where the alkylene oxide adduct ofaniline is tojbe added ot the viscose, the amount of the adduct which isincorporated in viscose must be at least about 0.2% by Weight of thecellulose in the viscose and mayvary up to about 4%, preferably, theamount varies from 0.5%

i to 2%. Lesser amounts do not result in the production of, products;consisting: entirely 'ofskin and greater amounts affect adversely thephysical properties. of .the*

products. Amounts within thepreferred range aremost efiective inenhancing the characteristics and properties 1 i of the products. Theadduct of aniline may be added at i H 3 any desired stage in theproduction of the viscose-such as in the preparation of the refined woodpulp forthe manufacture of viscose, before or gduringthe shredding of;the alkali cellulose, to the .x-anthated cellulose, while Y g u q ..-bre 9r;-'afts fi rat n fliidus is-r tsra e slt a t th v sel ess: Xamh t edissolved in the caustic solution-and prior to-filtration endthecomposition of me sin Ba ,li nai eifit 1 PYi a e.hny ran innate? stateone .7

cellulose, the particular source of the cellulose being selected for theultimate use of the regenerated cellulose product. The caustic sodacontent may be from about 4% to about 8% and the carbon disulfidecontent may be from about 30% to about 50% based upon the weight of thecellulose. The modified viscose, that is, a viscose containing the smallamount of adduct, may have a salt test above about 7 and preferablyabove about 9 at the time of spinning or extrusion.

In order to obtain the improvements enumerated hereinbefore, it isessential that the composition of the spinning bath be maintained withina well defined range. The presence of the alkylene oxide adducts ofaniline in the viscose or in the spinning bath combined with theselimited spinning baths results in the production of yarns of improvedproperties such as high tenacity, high abrasion resistance, high fatigueresistance and consisting of filaments composed entirely of skin.

Generically and in terms of the industrial art, the spinning bath is alow acid-high zinc spinning bath. The bath should contain from about 10%to about 25% sodium sulfate and from about 3% to about 15% zinc sulfate,preferably from 15% to 22% sodium sulfate and from 4% to 9% Zincsulfate. Other metal sulfates such as iron, manganese, nickel and thelike may be present and may replace some of the zinc sulfate. Thetemperature of the spinning bath may vary from about 25 C. to about 80C., preferably between about 45 C. and about 70 C. In the production ofthe all skin type filaments, the temperature of the spinning bath is notcritical, however, as is well known in the conventional practice in theart, certain of the physical properties such as tensile strength varydirectly with the temperature of the spinning bath. Thus, in theproduction of filaments for tire cord purposes in accordance with themethod of this invention, the spinning bath is preferably maintained ata temperature between about 55 C. and 65 C. so as to obtain the desiredhigh tensile strength.

The acid content of the spinning bath is balanced against thecomposition of the viscose. The lower limit of the acid concentration,as is well known in the art, is just above the slubbing point, that is,the concentration at which small slubs of uncoagulated viscose appear inthe strand as it leaves the spinning bath. For commercial operations,the acid concentration of the spinning bath is generally maintainedabout 0.4% to 0.5% above the slubbing point. For any specific viscosecomposition, the acid concentration of the spinning bath must bemaintained above the slubbing point and below the point at which theneutralization of the caustic of the viscose is sufficiently rapid toform a filament having a skin and core.

There is a maximum acid concentration for any specific viscosecomposition beyond which the neutralization is sufiiciently rapid toproduce filaments having a skin and core. For example, in general, theacid concentration of the spinning baths which are satisfactory for theproduction of the all skin products from a 7% cellulose, 6%caustic-viscose and containing the adducts of aniline lies between aboutand about 7.8%. The acid concentration may be increased as the amount ofadduct is increased and also as the salt test of the viscose isincreased. There is an upper limit, however, for the acid concentrationbased upon the amount of modifier and the concentration of caustic inthe viscose. All skin products cannot be obtained if the acidconcentration is increased above the maximum value although the amountof the adduct of aniline is increased beyond about 4%, based on theweight of the cellulose in the viscose, while other conditions aremaintained constant. Increasing the caustic soda content of the viscosebeyond about 8% is uneconomical for commercial production methods. Forexample, a viscose containing about 7% cellulose, about 6% caustic soda,about 41% carbon disulfide based on the weight of the cellulose, 1%,based on the weight of the cellulose, of an ethylene oxide adduct ofaniline containing about 6 ethylene oxide units per molecule and havinga salt test of about 10 when extruded into spinning baths containing 16to 20% sodium sulfate, 4 to 8% zinc sulfate and sulfuric acid not morethan about 7.8%, results in the production of all skin filaments. Lesseramounts of sulfuric acid may be employed. Greater amounts of sulfuricacid result in the production of products having skin and core. Alowering of the amount of adduct of aniline, the lowering of the causticsoda content or the lowering of the salt test of the viscose reduces themaximum permissible acid concentration for the production of all skinfilaments. It has been determined that the maximum concentration of acidwhich is permissible for the production of all skin products is about1.35 times the percentage caustic soda content of the viscose and ispreferably held between about 1.15 and 1.25 times the percentage causticsoda content of the viscose. Thus, for a viscose containing 8% causticsoda, the maximum acid content of the bath should not exceed about 8%1.35 or about 10.8%.

The presence of the adducts of aniline in the viscose retards thecoagulation and, therefore, the amount of adduct employed must bereduced at high spinning speeds. Thus, for optimum physicalcharacteristics of an all skin yarn formed from a viscose as above andat a spinning speed of about 50 meters per minute, the adduct isemployed in amounts within the lower portion of the range, for-example,about 0.5%. The determination of the specific maximum and optimumconcentration of acid for any specific viscose, spinning bath andspinning speed is a matter of simple experimentation for those skilledin the art. The extruded viscose must, of course, be immersed ormaintained in the spinning bath for a period sufiicient to effectrelatively complete coagulation of the viscose, that is, the coagulationmust be sutficient so that the filaments will not adhere to each otheras they are brought together and withdrawn from the bath.

In the production of filaments for such purposes as the fabrication oftire cord, the filaments are preferably stretched after removal from theinitial coagulating and regenerating bath. From the initial spinningbath, the filaments may be passed through a hot aqueous bath which mayconsist of hot water or a dilute acid solution and may be stretched fromabout 70% to about 120%, preferably between and Yarns for other textilepurposes may be stretched as low as 20%. The precise amount ofstretching will be dependent upon the desired tenacity and otherproperties and the specific type of product being produced. It is to beunderstood that the invention is not restricted to the production offilaments and yarns but it is also applicable to other shaped bodiessuch as sheets, films, tubes and the like. The filaments may then bepassed through a final regenerating bath which may contain from about 1%to about 5% sulfuric acid and from about 1% to about 5% sodium sulfatewith or without small amounts of zinc sulfate if regeneration has notpreviously been completed.

The treatment following the final regenerating bath, or the stretchingoperation where regeneration has been completed, may consist of awashing step, a desulfurizing step, the application of a finishing orplasticizing material and drying before or after collecting, or mayinclude other desired and conventional steps such as bleaching and thelike. The treatment after regeneration will be dictated by the specifictype of shaped body and the proposed use thereof.

Regenerated cellulose filaments prepared from viscose containing thesmall amounts of the water-soluble alkylene oxide adducts of aniline andspun in the spinning baths of limited acid content have asmooth ornon-crcnulated surface and consist substantially entirely of skin. causeof the uniformity of structure throughout the filament, the swelling andstaining characteristics are uniform throughout the cross-section of thefilament. Fila ments produced pursuant to this invention and consistingentirely of skin have a high toughness and a greater flexing life thanfilaments as produced according to prior methods which may be attributedby the uniformity in skin structure throughout the filament. Althoughthe twisting of conventional filaments, as in theiproduction of tirecord, results in an appreciable loss of tensile strength, there isappreciably less loss in tensile strength in the production of twistedcords from the filaments consisting entirely of skin. Filaments preparedfrom viscose containing the alkylene oxide adducts of aniline have ahigh tensile strength as com-pared to normal regenerated cellulosefilaments, have superior abrasion and fatigue resistance characteristicsand have a high flex-life. Such filaments are highly satisfactory forthe production of cords for the reinforcement of rubber products such aspneumatic tire casings, but the filaments are not restricted to suchuses and may be used for other textile applications.

Like improvements in the chaarcterist-ics and properties of the productsare also obtained by incorporating the alkylene oxide adducts of anilinein thespinning bath in place of adding the adduct to the viscose. It isessential that the composition of the spinning bath, particularly theacid concentration be maintained within the limits set forthhereinbefore. In order to produce products consisting of all skin, theamount of the alkylene oxide adduct of aniline dissolved in the spinningbath must beat least about 0.05% by weight and isp'referably maintainedat about 0.1%; The upper limit does not appear to be critical as in theincorporation of the adducts in the viscose. The upper limit isdependent upon the solubility of the particular adduct and by economicconsiderations since amounts exceeding about 0.2% are not more effectivein improving thepropenties of the products.

It is obvious that the adducts may be added to both the viscose nad thespinning bath, if desired. In such instance, it is also essential tomaintain the amountsof the adduct in the viscose and in the spinningbath, and the composition of the spinning bath within the statedlimits.The all skin products of improved properties are obtained only when thespinning operation in the presence of the alkylene oxide adductsofaniline is carried out within the spinning bath composition as setforth hereinbefore. 1

The invention may be illustrated by reference to the preparation [ofregenerated cellulose filaments from a viscose containing about 7%cellulose, about 6%.caustic soda, and having a total carbon disulfidecontent of about 41% based on the weight of the cellulose. Theviscosesolutions were prepared by xanthating alkali cellulose by theintroduction of 36%' carbon disulfide based on the weight of thecellulose and churning for about 2 hours. The cellulose xanthate wasthen dissolved in caustic soda solution. An additional 5% carbondisulfide was then added to the mixer and the mass mixed for about onehour. The viscosewas then allowed to ripen for about 30 hours at 18 C.In those instances where the modifier was incorporated in the viscose,the desired amount of an ethylene oxide adduct of aniline was added tothe solution and mixed for about /2 hour before allowing the viscose toripen.

Example 1 Approximately 1% (based on the weight of the cellulose) of anethylene oxide adduct of anilinecontaining about 6 ethylene oxide unitsper molecule of aniline was added to and incorporated in the viscose asdescribed above. The viscose employed in the spinning of filaments had asalt test of 10. The viscose was extruded through a spinneret to form a1650 denier, 720 filament cord at a rate of about 22 meters per minute.The coagulating and regenerating bath was maintained at a temperature ofabout 60 C. and contained 7.1%sulfurie acid, 8% zinc sulfate and 17%sodium sulfate. The cord was stretched about 90%, Washed free of acidsand salts by treatment with water at about 95 C. on thread advancingreels, dried and collected on cones. j w 1 1 The individual filamentshave a smooth, non-crenulated exterior surface and consist entirely ofskin, no core being detectable at high magnification (e.g. 1500 Thefilaments of 'a control yarn spun with the same viscose but without theaddition of the modified agent and spun under the same conditions,exhibit a very irregular and serrated surface and are composed of aboutskin and the balance core with a sharp line of demarkation between theskin and core. Other physical properties are set forth in the tablewhich follows the examples.

Example 2 A viscose solution as described above (no adduct added) havinga salt test of 10.7 was spun into a 210 denier, 120 filament yarn byextrusion into a spirming bath containing 7.7% sulfuric acid, 8% zincsulfate, 17% sodium sulfate and 0.1% of an ethylene oxide adduct ofaniline containing about 6 ethylene oxide units. per molecule ofaniline. The bath was maintained at 60 C. and the extrusion rate wasabout 22 meters per minute.

The filaments were passed through .a hot water bath main:

tained at about C. and stretched about 82%. The yarn was collected in aspinning box, washed free of acid and salts and dried.

The filaments have a smooth, non-crenulated surface and consist entirelyof skin while control filaments have a very irregular and serratedsurface and consist of about 75% skin and the balance corewith a sharpline of de markation between the skin and core. Other physicalcharacteristics are set forth in the table which follows the examples.

Example 3 To a viscose as described above, there was added 1%, based onthe weight of the cellulose in the viscose, of

an ethylene oxide adduct of aniline containing 6 ethylene oxide unitsper molecule of aniline. The viscose had a salt test of 10.7 and wasspuninto a 210 denier, filament yarn by extnusion into a spinning bathcontaining 7.7% sulfuric acid, 8.3%- zinc sulfate, 17% sodium sulfate,and 0.1% of an ethylene oxide adduct of aniline containing 6 ethyleneoxideunitsper molecule ofaniline. The bath was maintained at 60 C. andthe extrusion rate was about 22 meters per minute. The filaments weresubsequently passed through a hot water-bath at 95 C. and stretchedabout 82%. The yarn was collected in a spinning box, washed free ofacids and salts and dried;

The individual filaments were readily distinguishable from controlfilaments in that they have a smooth, non-' crenulated surface andconsist entirely, of skin whilethe 7 table which follows the examples.

Example 4 As a control for the foregoing examples, a viscose solution,prepared as described above, having a salt test of 10 was spun into a210 denier, 120 filament yarn by extrusion into a bath containing 7.5%sulfuric acid, 8%'

zinc sulfate and 18% sodium sulfate. 7 The bath was maintained at atemperature of about 60 C. The extnusion rate was about 22 meters perminute. The water bath was maintained at a temperature of about 95" C.

and, the filaments were stretched 827%; while passing through the hotwater. The yarn was'collected in a spin- 'ning box, washed free of acidand salts and dried,

. The individual filamentsfhave a very irregular and serrated surfaceand consist of about 75 skin and the balance core with a sharp line ofdemarkation between I the skin and the core. Other characteristics areset forth in the table which follows:

Although the tenacity and elongation are the only properties set forth,they have been chosen because of the ease and simplicity with which suchproperties may be determined. In some instances, products made inaccordance with this invention do not exhibit large or greatimprovements in tenacity and elongation (Example 3), however, theproducts consists of a smooth-surfaced, all skin structure and possessimproved abrasion resistance, flex-life and other properties asdisclosed hereinbefore.

One of the properties of viscose rayon which has limited its uses is itsrelatively high cross-sectional swelling when wet with water, thisswelling amounting to from about 65% to about 80% for rayon produced byconventional methods. Rayon filaments produced in accordance with themethod of this invention have an appreciably lower cross-sectionalswelling characteristic, the swelling amounting to from about 45% toabout 60%.

The modifier of this invention may be added to any desired viscose suchas those normally used in industry, the specific viscose composition setforth above, being merely for illustrative purposes. The alkylene oxideadduct of aniline may be added at any desired stage in the production ofthe viscose and may be present in the cellulosic raw material althoughit may be necessary to adjust the amount present to produce a viscosehaving the proper proportions of the adduct at the time of spinning.

The term skin is employed to designate that portion of regeneratedcellulose filaments which is permanently stained or dyed by thefollowing procedure: A microtome section of one or more ofthe filamentsmounted in a wax block is taken and mounted on a slide with Meyersalbumin fixative. After dewaxing in xylene, the section is placed insuccessive baths of 60% and 30% alcohol for a few moments each, and itis then stained in 2% aqueous solution of Victoria Blue BS conc.(General Dyestuffs Corp.) for 1 to 2 hours. At this point, the entiresection is blue. By rinsing the section first in distilled water andthen in one or more baths composed of 10% water and 90% dioxane for aperiod varying from to 30 minutes depending on the particular filament,the dye is entirely removed from the core, leaving it restricted to theskin areas.

While preferred embodiments of the invention have been disclosed, thedescription is intended to be illustrative and it is to be understoodthat changes and variations may be made without departing from thespirit and scope of the invention as defined by the appended claims.

I claim:

1. In a method of producing shaped bodies of regenerated celluloseconsisting substantially entirely of skin, the step which comprisesextruding viscose into an aqueous spinning bath in the presence of awater-soluble substance selected from the group consisting ofwatersoluble N,N-di(beta-hydroxyalkyl)anilines, water-solubleN-mono(omega-hydroxy polyoxyalkylene)anilines, watersolubleN,N-di(omega-hydroxy polyoxyalkylene)anilines and mixtures thereof, thehydroxyalkyl and the oxyalkyl ene groups containing at least 2 carbonatoms, the bath containing from about to 25% sodium sulfate, from about3% to zinc sulfate and sulfuric acid, the percentage sulfuric acidcontent of the spinning bath exceeding the slubbing point but notexceeding about 1.35

8 times the percentage caustic soda content of the viscose, thewater-soluble substance being present in an amount of from about 0.2% toabout 4%, based upon the weight of the cellulose in the viscose, whenpresent in the viscose and of at least about 0.05%, based upon theweight of the spinning bath, when present in the spinning bath.

2. The step in the method as defined in claim 1 wherein the selectedsubstance is from the group consisting of Water-solubleN,N-di(beta-hydroxyethyl)aniline, watersoluble N-mono(omega-hydroxypolyoxyethylene)aniline, water-soluble N,N-di(omega-hydroxypolyoxyethylene)aniline and mixtures thereof, the N-substituted anilinescontaining from 2 to 30 ethylene oxide units per molecule of aniline.

3. The steps in the method of producing shaped bodies of regeneratedcellulose consisting substantially entirely of skin, the steps whichcomprise adding to and incorporating in a viscose from about 0.2% toabout 4% of a water-soluble substance selected from the group consistingof water-soluble N,N-di(beta-hydroxyalkyl)anilines, water-solubleN-mono(omega-hydroxy polyoxyalkylene)anilines, water-solubleN,N-di(omega-hydroxy polyoxyalkylene)anilines and mixtures thereof, thehydroxyalkyl and the oxyalkylene groups containing at least 2 carbonatoms, base upon the weight of the cellulose in the viscose, theN-substituted anilines containing from about 2 to about 50 ethyleneoxide units per molecule of aniline, and extruding the viscose into anaqueous spinning bath containing from about 10% to 25% sodium sulfate,from about 3% to 15% zinc sulfate and sulfuric acid, the percentagesulfuric acid content of the bath exceeding the slubbing point but notexceeding about 1.35 times the percentage caustic soda content of theviscose.

4. The method of producing shaped bodies of regenerated celluloseconsisting substantially entirely of skin which comprises adding to andincorporating in a viscose from about 0.5% to about 2%, based upon theweight of the cellulose in the viscose, of a substance selected from thegroup consisting of water-soluble N,N-di(beta-hydroxyethyl)aniline,water-soluble N-mono(ornega-hydroxy polyoxyethylene)aniline,water-soluble N,N-di- (omega-hydroxy polyoxethylene)aniline and mixturesthereof, the N-substituted anilines containing from 2 to 30 ethyleneoxide units per molecule of aniline, ripening the viscose to a saltpoint of not less than 9 and extruding the viscose into an aqueousspinning bath containing from about 16% to about 20% sodium sulfate,from about 4% to about 9% zinc sulfate and sulfuric acid, the sulfuricacid content of the spinning bath exceeding the slubbing point but notexceeding about 7.8%.

5. The method of producing shaped bodies of regenerated celluloseconsisting entirely of skin which comprises forming an aqueous spinningbath containing in solution from about 10% to 25% sodium sulfate, fromabout 3% to 15% zinc sulfate, at least about 0.05% of a substanceselected from the group consisting of water solubleN,N-di(beta-hydroxyalkyl)anilines, water-soluble N-mono(omega-hydroxypolyoxyalkylene)anilines, watersoluble N,N-di(omega-hydroxypolyoxyalkylene) anilines and mixtures thereof, the hydroxyalkyl and theoxyalkylene groups containing at least 2 carbon atoms, and sulfuricacid, and extruding viscose into the spinning bath, the sulfuric acidcontent of the bath exceeding the slubbing point but not exceeding about7.8%.

6. The method as defined in claim 5 wherein the selected substance isfrom the group consisting of water-solubleN,N-di(beta-hydroxyethyl)aniline, water-soluble N-mono- (omega-hydroxypolyoxyethylene)anilinc, water-soluble N,N-di(omega-hydroxypolyoxyethylene) aniline and mixtures thereof. the N-substitutedanilines containing from 2 to 30 ethylene oxide units per molecule ofaniline.

7. An aqueous spinning bath for the production of regenerated celluloseproducts consisting substantially entirely of skin from viscosecontaining from about 10% to 25% sodium sulfate, from about 3% to 15%zinc sul acid, the percentage of sulfuric acid not exceeding about 8. Anaqueous spinning bath as degned in claim 7 wherein the selectedsubstance is from the group consisting of water-solubleN,N-di(beta-hydroxyethyl)ani line, water-soluble N-mono(omega-hydroxypolyoxyethylene)aniline, water-soluble N,N-di(omega-hydroxy polyoxyethylene)aniline and mixtures thereof, the N-substituted anilinescontaining from 2 to 30 ethylene oxide units per molecule of aniline.

References Cited in the file of this patent UNITED STATES PATENTS2,125,031 Polak July 26, 1938 2,312,152 Davis Feb. 23, 1943 2,373,712Schlosser Apr. 17, 1945 2,593,466 MacLaurin Apr. 22, 1952

1. IN A METHOD OF PRODUCTING SHAPED BODIES OF REGENERATED CELLULOSECONSISTING SUBSTANTIALLY ENTIRELY OF SKIN, THE STEP WHICH COMPRISESEXTRUDING VISCOSE INTO AN AQUEOUS SPINNING BATH IN THE PRESENCE PF AWATER-SOLUBLE SUBSTANCE SELECTED FROM THE GROUP CONSISTING OFWATERSOLUBLE N,N-DI-(BETA-HYDROXYALKYL)ANILINES, WATER-SOLUBLEN-MONO(OMEGA-HYDROXY POLYOXYALKYLENE)ANILINES, WATERSOLUBLEN,N-DI-(OMEGA-HYDROXY POLYOXYALKYLENE)ANILINES AND MIXTURES THEREOF, THEHYDROXALKYL AND THE OXYALKYLENE GROUPS CONTAINING AT LEAST 2 CARBONATOMS, THE BATH CONTAINING FRON ABOUT 10% TO 25% SODIUM SULFATE FROMABOUT 3% TO 15% ZINC SULFATE AND SULFURIC ACID, THE PERCENTAGE SULFURICACID CONTANT OF THE SPINNING BATH EXCEEDING THE SLUBBING POINT BUT NOTEXCEEDING ABOUT 1.35 TIMES THE PERCENTAGE CAUSTIC SODA CONTENT OF THEVISCOSE, THE WATER-SOLUBLE SUBSTANCE BEING PRESENT ON AN AMOUNT OF FROMABOUT 0.2% TO ABOUT 4% BASED UPON THE WEIGHT OF THE CELLULOSE IN THEVISCOSE, WHEN PRESENT IN THE VISCOSE AND OF AT LEAST ABOUT 0.35%, BASEDUPON THE WEIGHT OF THE SPINNING BATH, WHEN PRESENT IN THE SPINNING BATH.